The present invention relates to a technique and to apparatus for reliably sampling biocidal gas contained in a reaction chamber of the type used to treat, to deactivate or to destroy viable microorganisms and insects as well as lifecycle forms through which such organisms evolve. More particularly, the invention is directed to an apparatus and method by which the biocidal gas in the treating or reaction chamber is effectively sampled at any optionally selected predetermined time in the processing cycle.
The present invention finds special utility in processing systems in which the sterilant gas used is a mixture of an alkylene oxide such as ethylene oxide or propylene oxide with an inert diluent gas such as a halogenated hydrocarbon or carbon dioxide. The inert diluent is commonly used in such systems to eliminate flammability and to prevent the development of explosive atmospheres.
Gaseous systems of the type described are widely used in order to reduce the concentration of viable organisms in many types of products including food products and pharmaceutical products. The use of ethylene oxide as an active "sterilization" agent has proven an attractive technique because the gas itself is highly volatile and leaves essentially no residues. Nor is it destructive to the many types of materials which require treatment. A principal technique by which the actual sterilization treatment is conducted is to introduce the material to be treated into a relatively large chamber (8'.times.8'.times.10') provided with suitable gas-tight doors, valving for introduction of sterilant gases, humidity control systems and heating tubes. The material having been introduced into the chamber, the latter is evacuated and then the sterilant gas mixture is introduced.
Typically, the gaseous mixture constitutes a mixture of ethylene oxide with a flourohydrocarbon such as trichloromonoflouromethane, dichlorodiflouromethane, and the like. The inherent flammability and potential explosiveness of ethylene oxide (in combination with air) is obviated through the incorporation of the inert flouro-chloro-hydrocarbon.
Since the effectiveness of the sterilization process using this type of gas mixture is dependent upon the proportional concentration of ethylene oxide in the gaseous mixture used, as well as the temperature and the exposure duration, it is most important to maintain accurate records of the concentration and composition of the sterilant gas mixture in the reaction chamber during the processing cycle. One technique has been to maintain a continuous monitoring of the gas composition by continuously sampling the gas in a flow system, the sampled gas being subjected to analysis using any preferred analytical techniques. However, in the continuous sampling procedure, the acquisition and transportation of the sample, while presenting component separation, has proved to be cumbersome and difficult. Additionally, the cost of the necessary "plumbing" has been high and there is a requirement that a highly trained technician be present at all times to carry out the necessary procedures. It is to the resolution and circumvention of these and other difficulties that the present invention is directed.